Fabrication, measurement and time decay of the electromagnetic properties of semi-solid water-based phantoms

This paper presents a complete and detailed description of the fabrication and measurement of the electromagnetic properties of water-based semi-solid phantoms with emphasis on the analysis of the time evolution of the complex permittivity of several samples stored in different conditions. A known recipe for a 2/3 muscle equivalent phantom is used as test material, and the several phantom sample properties are measured with an in-house developed coaxial probe technique. It is shown that the storing condition is of paramount importance to extend the lifetime of a given phantom. This behavior stems from the way the storing condition affects the water evaporation rate of the sample. In particular, while an unprotected sample can preserve its electromagnetic properties only for a few days, a very well-sealed one can last at least up to a year.info:eu-repo/semantics/publishedVersio

Limites fundamentais em antenas impressas pequenas

O objectivo desta comunicação é a análise de antenas impressas miniaturizadas utilizadas nos modernos e pequenos terminais portáteis dos sistemas de comunicações móveis. Começa-se pelo estudo do comportamento de antenas em geral, apresentando limites físicos fundamentais no que diz respeito à relação entre dimensão, ganho e largura de banda. É mostrado que a largura de banda, ganho e volume de uma antena estão relacionadas entre si e que o produto ganho - largura de banda é proporcional ao volume da antena. Apresentam-se ainda resultados de protótipos construídos anteriormente, e mostra-se que estes apresentam um desempenho que se encontra afastado do limite teórico, o que parece indicar que podem ainda ser mais optimizados.info:eu-repo/semantics/publishedVersio

O Livro de Horas do Museu de Angra do Heroísmo

UIDB/00749/2020 UIDP/00749/2020 UIDB/00019/2020The main objective of this study is to present the Book of Hours that is kept in the Museum of Angra do Heroísmo. It is an illuminated manuscript, practically unknown until now, which was acquired by this institution, in 1979, from a well-known antique bookseller in Lisbon. Presumably, it was illuminated at the end of the 15th century, or in the first years of the following century, keeping only eight illuminated folios. From its content, we highlight the uniqueness of some festivities in the calendar, the inclusion of small offices, such as the Hours of the Conception of the Virgin and the Hours of St. Barbara, and the presence of two illuminated folios in the Office of the Dead. The ownership marks allowed to reconstruct part of its history and to identify some of its previous owners.publishersversionpublishe

Planarne male višefrekvencijske antene oblika invertiranog F za ručne pokretne komunikacijske uređaje

Three small multi-band planar inverted-F antenna (PIFA) elements are presented. They have been developed to be used in future small multi-standard handsets. Mobile communication (GSM1800, UMTS), wireless local area network (WLAN) (IEEE 802.11b, HiperLAN2) and wireless personal area network (WPAN) (Bluetooth) standards have been envisaged. A double layer structure with an air gap is used, to provide the required large bandwidth. Small ground planes with 100 × 40 mm2 and 60 × 40 mm2 are used representing nowadays one piece and two pieces small handsets. Prototypes have been designed, fabricated and tested. Good agreement has been obtained between numerical simulations and experimental results.U radu su prikazane tri izvedbe planarnih malih višefrekvencijskih antena oblika invertiranog F. Antene su razvijene za primjenu u ručnim uređajima za pokretne komunikacije koji će raditi u više različitih radijskih komunikacijskih sustava. U razmatranje su uzeti sustavi pokretnih komunikacija (GSM1800, UMTS), radijske lokalne mreže (WLAN) (IEEE 802.11b, HiperLAN2) i radijske mreže za osobne potrebe (WPAN) (Bluetooth). U izvedbi antena primijenjena je dvoslojna izvedba ispunjena zrakom kako bi se postigla željena širina pojasa. Antene su smješene na osnovne uzemljene površine s izmjerama 100 mm × 40 mm i 60 mm × 40 mm što odgovara izmjerama nepreklopivih i preklopivih ručnih komunikacijskih uredaja. Sve su tri antene projektirane, izrađene i ispitane mjerenjima. Postignuto je dobro podudaranje izračunanih i izmjerenih vrijednosti parametara antena

Wideband Printed Planar Monopole Antenna Element for Wearable Application

The implementation of a wideband printed monopole antenna near a metallic shield is presented. A wearable antenna system application to probe the electromagnetic field, with frequency in the range 0.7-3.5 GHz (5:1 bandwidth), incident on a professional user is envisaged. A lossy foam layer is used between the shield and the antenna to absorb the shield reflection and avoid narrowing the bandwidth

On-body off-body dual mode microstrip antenna for Body Area Network applications

This paper describes the design, fabrication and test of a novel dual mode, on-body and off-body, planar microstrip antenna for Body Area Networks applications. The on-body antenna is obtained with a microstrip ring operating at a higher order mode while the off-body antenna is obtained with a meandered microstrip antenna. The antennas are fed separately but share a common ground plane and are disposed so that the occupied area is minimized.info:eu-repo/semantics/publishedVersio

On-body transmission performance of a novel dual-mode wearable microstrip antenna

The path loss established between several wearable antenas placed on a tissue-equivalent phantom is investigated through numerical simulations and measurements. The on-body performance of a previously proposed dual-mode wearable textile antenna, designed to operate in the 2.45 GHz industrial, scientific and medical band, is evaluated and compared with a wearable textile patch antenna. Simulation results of a _/4 resonant wire monopole are also presented to serve as a reference. Five different scenarios for the location of the transmitting and receiving antennas are analyzed: one with line of sight (LOS), two with non- LOS (NLOS), and the remaining two in the transition between LOS and NLOS. The transmission results are evaluated with the antenas mounted on the surface of a homogeneous phantom with 2/3 muscle properties mimicking the shape and physical macroscopic properties of a human torso. A general good agreement is obtained between numerical simulation and experimental results. It is shown that in the NLOS scenario, the proposed antenna has an equivalent path loss only about 3.4 dB higher than the monopole and about 10 dB lower than the patch.info:eu-repo/semantics/publishedVersio

A Dual-Mode Single-Band Wearable Microstrip Antenna for Body Area Networks

Design, fabrication, and test of a novel single-band wearable antenna with dual-mode operation (on-body and offbody) for body area network’s applications in the 2.45 GHz industrial scientific and medical band are presented. The on-body mode is achieved with a microstrip ring while the off-body mode is obtained with a compact meanderedmicrostrip patch placed inside the ring. The two antennas are fed separately but share a common ground plane and use only fabricmaterials facilitating the integration into the user’s clothes. The antenna operation is characterized when placed on a phantom mimicking a human torso. Input match, mutual coupling, radiation pattern, radiation efficiency, and path loss measurements are presented and show good agreement with simulations.info:eu-repo/semantics/publishedVersio

Wideband, Wearable, Printed Monopole Antenna System for Integration into an Electromagnetic Radiation Evaluation Device

This paper describes the design steps carried out to prove the concept of a wideband monopole antenna system to be used in a wearable device conceived for the evaluation of electromagnetic field radiation. Such a device is envisaged to be integrated into protective vests worn by professional users in their working space environment as part of intelligent multi-risk protection. Initially, the main characteristics of a simple straight monopole are reviewed to serve as a reference. A modified octagonal monopole antenna element is introduced, and a two dual-linearly polarized configuration of such monopoles is designed, fabricated, and tested to be used in the frequency range of 0.7–3.5 GHz. The expected radiation characteristics (input reflection coefficient and isolation between vertically and horizontally polarized ports) are confirmed experimentally. The effects of a thick lossy foam substrate layer used to mitigate the presence of the metal shield, employed in the vest lining as a Faraday cage protection, are analyzed both by simulation and experimentally. Finally, electromagnetic simulations are carried out to confirm that a system of five dual-linearly polarized monopole elements located in the chest, shoulders, back, and helmet of the user can provide an adequate estimation of the incident electromagnetic field radiation